U.S. patent number 9,340,272 [Application Number 14/321,374] was granted by the patent office on 2016-05-17 for altitude control via adjustment to mass of air in bladder within lift-gas filled envelope.
This patent grant is currently assigned to Google Inc.. The grantee listed for this patent is Google Inc.. Invention is credited to Clifford L. Biffle, Richard Wayne DeVaul.
United States Patent |
9,340,272 |
DeVaul , et al. |
May 17, 2016 |
Altitude control via adjustment to mass of air in bladder within
lift-gas filled envelope
Abstract
This disclosure relates to the use of a method for adjusting an
altitude of variable-buoyancy vehicle, such as an aerostatic
balloon. The method includes determining a target mass for a
variable-buoyancy vehicle, where the target mass is based on a
target altitude for the variable-buoyancy vehicle. Additionally,
the method includes adding a first mass to the variable-buoyancy
vehicle. The mass added is less than a difference between the
target mass and a current mass. The method also includes adding a
second mass to the variable-buoyancy vehicle in response to a
decrease in an internal pressure of the variable-buoyancy vehicle
caused by adding the first mass. Further, adding the second mass
makes a current mass of the variable-buoyancy vehicle approximately
equal to the target mass.
Inventors: |
DeVaul; Richard Wayne (Mountain
View, CA), Biffle; Clifford L. (Mountain View, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Google Inc. |
Mountain View |
CA |
US |
|
|
Assignee: |
Google Inc. (Mountain View,
CA)
|
Family
ID: |
55920004 |
Appl.
No.: |
14/321,374 |
Filed: |
July 1, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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61882393 |
Sep 25, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B64B
1/62 (20130101); B64B 1/60 (20130101); B64B
1/70 (20130101) |
Current International
Class: |
B64B
1/58 (20060101); B64B 1/62 (20060101); B64B
1/70 (20060101) |
Field of
Search: |
;244/98 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: O'Hara; Brian M
Assistant Examiner: Dixon; Keith L
Attorney, Agent or Firm: McDonnell Boehnen Hulbert and
Berghoff LLP
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
The present application claims priority to U.S. Provisional Patent
Application Ser. No. 61/882,393, filed on Sep. 25, 2013, the entire
contents of which are herein incorporated by reference.
Claims
What is claimed is:
1. A method for adjusting a variable-buoyancy vehicle comprising:
determining a target mass for a variable-buoyancy vehicle having an
initial internal pressure and an initial altitude, based on a
target altitude for the variable-buoyancy vehicle, wherein the
target altitude is lower than the initial altitude; adding a first
mass of air to the variable-buoyancy vehicle, wherein the mass
added is less than a difference between the target mass and an
initial mass, and wherein the mass added causes an internal
pressure of the variable-buoyancy vehicle to increase; and in
response to in the internal pressure of the variable-buoyancy
vehicle decreasing below the initial internal pressure based on a
current altitude of the variable-buoyancy vehicle being lower than
the initial altitude, adding a second mass of air to the
variable-buoyancy vehicle, wherein the pressure of the
variable-buoyancy vehicle decreased based on the first adding mass,
wherein the second mass added makes a current mass of the
variable-buoyancy vehicle approximately equal to the target
mass.
2. The method of claim 1, further comprising determining the
internal pressure of the variable-buoyancy vehicle after adding the
first mass.
3. The method of claim 1, wherein the decrease in the internal
pressure has an associated delay time.
4. The method of claim 3, wherein the second mass is added after
the delay time.
5. The method of claim 2, wherein the second mass is added in
response to the internal pressure falling below a threshold.
6. The method of claim 5, wherein the threshold is selected based
on a power consumption of a pump of the variable-buoyancy
vehicle.
7. The method of claim 5, wherein the threshold is selected based
on an inflection point of a pressure curve of the internal pressure
of the variable-buoyancy vehicle.
8. A balloon comprising: an envelope configured to hold air; a
bladder configured to hold lift gas, wherein the bladder is located
within the envelope; a control unit configured to add or remove air
from the envelope in order to change a mass of air in the envelope;
and a processing unit configured to: determine a target mass for
the balloon, based on a target altitude for the balloon; cause the
control unit to add a first mass of air to the balloon, wherein the
mass added is less than a difference between the target mass and a
current mass; and in response to a decrease in an internal pressure
of the balloon, cause the control unit to add a second mass of air
to the balloon, wherein the pressure of the balloon decreased based
on the first adding mass, wherein the second mass of air added
makes a current mass of the balloon approximately equal to the
target mass.
9. The balloon of claim 8, wherein the processing unit is further
configured to determine the internal pressure of the aerostatic
balloon after adding the first mass of air.
10. The balloon of claim 8, wherein the decrease in ihe internal
pressure has an associated delay time.
11. The balloon of claim 10, wherein the processing unit causes the
second mass of air to be added after the delay time.
12. The balloon of claim 9, wherein the processing unit causes the
second mass of air to be added in response to the internal pressure
falling below a threshold.
13. The balloon of claim 12, wherein the threshold is selected
based on a power consumption of the control unit of the
balloon.
14. An article of manufacture including a non-transitory
computer-readable medium having stored thereon program instructions
that, if executed by a processor in a balloon-control system, cause
the balloon-control system to perform operations comprising:
determining a target mass for a variable-buoyancy vehicle, based on
a target altitude for the variable-buoyancy vehicle; adding a first
mass of air to the variable-buoyancy vehicle, wherein the mass
added is less than a difference between the target mass and a
current mass; and in response to a decrease in an internal pressure
of the variable-buoyancy vehicle, adding a second mass of air to
the variable-buoyancy vehicle, wherein the pressure of the
variable-buoyancy vehicle decreased based on the first adding mass,
wherein the second mass of air added makes a current mass of the
variable-buoyancy vehicle approximately equal to the target
mass.
15. The article of manufacture of claim 14, further comprising
determining the internal pressure of the variable-buoyancy vehicle
after adding the first mass of air.
16. The article of manufacture of claim 14, wherein the decrease in
the internal pressure has an associated delay time.
17. The article of manufacture of claim 16, wherein the second mass
of air is added after the delay time.
18. The article of manufacture of claim 15, wherein the second mass
of air is added in response to the internal pressure falling below
a threshold.
19. The article of manufacture of claim 18, wherein the threshold
is selected based on a power consumption of a pump of the
variable-buoyancy vehicle.
20. The article of manufacture of claim 14, wherein the
variable-buoyancy vehicle is an aerostatic balloon.
Description
BACKGROUND
Computing devices such as personal computers, laptop computers,
tablet computers, cellular phones, and countless types of
Internet-capable devices are increasingly prevalent in numerous
aspects of modern life. As such, the demand for data connectivity
via the Internet, cellular data networks, and other such networks,
is growing. However, there are many areas of the world where data
connectivity is still unavailable, or if available, is unreliable
and/or costly. Accordingly, additional network infrastructure is
desirable.
SUMMARY
In order to adjust the altitude of a variable-buoyancy vehicle,
such as a balloon, air is either added or removed from inside the
variable-buoyancy vehicle. To increase altitude, air is removed; to
decrease altitude, air is added. Air is added to the balloon via a
pumping mechanism. The pumping mechanism uses a portion of the
energy reserve of the balloon. Therefore, an efficient method of
adding air may help extend the energy resources of the balloon.
In one aspect, the present disclosure features a method for
adjusting an altitude of variable-buoyancy vehicle. The method
includes determining a target mass for a variable-buoyancy vehicle,
where the target mass is based on a target altitude for the
variable-buoyancy vehicle. Additionally, the method includes adding
a first mass to the variable-buoyancy vehicle. Adding the first
mass causes both a pressure increase inside the variable-buoyancy
vehicle and the altitude of the variable-buoyancy vehicle to
decrease. The mass added is less than a difference between the
target mass and a current mass. The method also includes adding a
second mass to the variable-buoyancy vehicle in response to a
decrease in an internal pressure of the variable-buoyancy vehicle
caused by adding the first mass. Further, adding the second mass
makes a current mass of the variable-buoyancy vehicle approximately
equal to the target mass.
In some embodiments, the method also includes determining the
internal pressure of the variable-buoyancy vehicle after adding the
first mass. The second mass is added in response to the internal
pressure falling below a threshold pressure. Additionally, the
threshold pressure may be selected based on a power consumption of
a pump of the variable-buoyancy vehicle. In other embodiments, the
method includes the decrease internal pressure having an associated
delay time and adding the second mass is after the delay time.
Further, in some embodiments, the variable-buoyancy vehicle may
take the form of an aerostatic balloon.
In a second aspect, the present disclosure features an aerostatic
balloon. The aerostatic balloon includes an envelope configured to
hold air and a bladder configured to hold lift gas. The bladder of
the aerostatic balloon is located within the envelope. The
aerostatic balloon also includes a control unit configured to add
or remove air from the envelope in order to change a mass of air in
the envelope. Further, the aerostatic balloon includes a processing
unit. The processing unit is configured to determine a target mass
for the aerostatic balloon, based on a target altitude for the
aerostatic balloon. Additionally, the processing unit is configured
to cause the control unit to add a first mass to the aerostatic
balloon, wherein the mass added is less than a difference between
the target mass and a current mass. Further, in response to a
decrease in an internal pressure of the aerostatic balloon, the
processing unit is configured to cause the control unit to add a
second mass to aerostatic balloon. The pressure of the aerostatic
balloon decreases based on the first adding mass and adding second
mass added makes a current mass of the variable-buoyancy vehicle
approximately equal to the target mass.
In some embodiments, the processing unit is further configured to
determine the internal pressure of the aerostatic balloon after
adding the first mass. The processing unit may be further
configured to add the second mass in response to the internal
pressure falling below a threshold. The threshold may be selected
based on a power consumption of the control unit of the aerostatic
balloon. In additionally embodiments, the decrease in the internal
pressure of the aerostatic balloon has an associated delay time.
The processing unit may be configured to add the second mass to be
after the delay time.
In a third aspect, the present disclosure features an article of
manufacture including a non-transitory computer-readable medium
having stored thereon program instructions that, if executed by a
processor in a balloon-control system, cause the balloon-control
system to perform operations. The operations include determining a
target mass for a variable-buoyancy vehicle, where the target mass
is based on a target altitude for the variable-buoyancy vehicle.
Additionally, the operations include adding a first mass to the
variable-buoyancy vehicle. The mass added is less than a difference
between the target mass and a current mass. The operations also
include adding a second mass to the variable-buoyancy vehicle in
response to a decrease in an internal pressure of the
variable-buoyancy vehicle caused by adding the first mass. Further,
operations include adding the second mass makes a current mass of
the variable-buoyancy vehicle approximately equal to the target
mass.
In some embodiments, the operations also include determining the
internal pressure of the variable-buoyancy vehicle after adding the
first mass. The second mass is added in response to the internal
pressure falling below a threshold pressure. Additionally, the
threshold pressure may be selected based on a power consumption of
a pump of the variable-buoyancy vehicle. In other embodiments, the
operations include the decrease internal pressure having an
associated delay time and adding the second mass is after the delay
time. Further, in some embodiments, the variable-buoyancy vehicle
may take the form of an aerostatic balloon.
In some examples, the operations may include balloon parameters
having an associated global location. Additionally, communicating
the fill-rate control plan may include communicating instructions
for changing the balloon parameters. In some embodiments, the
communication may be performed wirelessly. Operations may also
include instructions for changing the balloon parameters, such as
instructions for operating an impeller powered by renewable
energy.
BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 illustrates a high-altitude balloon, according to an
embodiment.
FIG. 2 illustrates a balloon network, according to an
embodiment.
FIG. 3 illustrates a centralized system for controlling a balloon
network, according to an embodiment.
FIG. 4 illustrates a balloon network that includes super-nodes and
sub-nodes, according to an embodiment.
FIG. 5 illustrates a method for the altitude control for a super
pressure aerostatic balloon.
FIG. 6 illustrates an example chart describing the internal
pressure and altitude of a balloon changing states.
FIG. 7 illustrates a functional block diagram of a computing
device, according to an embodiment.
FIG. 8 illustrates a computer program product, according to an
embodiment.
DETAILED DESCRIPTION
I. Overview
Illustrative embodiments can implement a method for adjusting an
altitude of a super pressure aerostatic balloon with a data network
of balloons, such as, for example, a mesh network of high-altitude
balloons deployed in the stratosphere. The method for adjusting the
altitude can reconfigure the altitude of a balloon in a way to
reduce energy usage, possibly operating in a balloon network, in
situations when the balloon network is needed or desired to
supplement a cellular network, among other situations. The balloon
network can be useful for supplementing the cellular network in
various scenarios. For example, the balloon network can be a useful
supplement when the cellular network has reached capacity. As
another example, the balloon network can be a useful supplement
when the cellular network provides insufficient coverage in a given
area.
In order to adjust the altitude of the balloon, air is either added
or removed from inside the balloon. Air is added to the balloon via
a pumping mechanism. However, the pumping mechanism uses a portion
of the energy reserve of the balloon and the energy reserve is a
precious resource for the balloon. Therefore, an efficient method
of adding may help extend the energy resources of the balloon. The
method for adjusting the altitude of the balloon includes
determining a target mass for the balloon based on a target
altitude for the balloon. Next, an amount of air is added to the
balloon with the pump. The amount of air added is less than the
amount needed for the balloon to equal the target mass. When the
mass is added, the pressure in the balloon increases, causing the
balloon to decrease altitude.
In response to the decrease in altitude, the internal pressure
within the balloon may fall. The internal pressure of the balloon
may fall enough to where the current pressure within the balloon is
less than initial pressure when the air was added. When the current
pressure is less than the initial pressure, the pump requires less
energy to add air inside the balloon; thus, there is an energy
savings. Therefore, at the time when the internal pressure is less
than the initial internal pressure, the balloon adds a second mass
to makes a current mass of the variable-buoyancy vehicle
approximately equal to the target mass.
To this end, an illustrative embodiment uses a central control
system that is configured to operate with the balloon network with
balloons flying at various altitudes. During operation of the
network, balloons may need to change altitude. However, in order to
have an extended period of flight, it may be desirable to use
renewable resources when adjusting the altitude of the balloon, and
if possible, to use renewable resources exclusively. Embodiments
also include the central control system changing the altitudes of
various balloons in a coordinated effort to form a balloon network,
as disclosed herein.
Traditional balloons may add or vent lift gas (e.g., helium) in
order to change altitude. However, when the helium supply is gone,
the balloon may not be able to increase altitude. Thus, the method
of optimally controlling altitude presented herein uses ambient air
so that there is not a finite supply for each balloon flight.
Further, the method of optimally controlling altitude may also
include adding or removing air using only a renewable power source,
such as solar power.
In one example embodiment, a balloon features solar charging units
configured to receive sunlight and convert it to energy. This
energy can be both stored in batteries and used to power components
of the balloon. The balloon also includes a control unit configured
to selectively add or remove air from the inside of the balloon.
Air that is added comes from the environment in which the balloon
is located. Further, the control unit is powered by the energy
stored in the batteries and provided by the solar charging units.
Thus, the balloon may be able to add or remove gas from the balloon
without depleting a gas source and by only using power that can be
renewed via sunlight.
Disclosed herein are methods and apparatuses configured to control
the altitude of a balloon that may form a portion of a
communication network. However, this disclosure is not limited to a
network of balloons and similar methods and apparatuses. The
disclosed methods and apparatuses may also function with a single
balloon, a high-altitude platform, or other variable-buoyancy
vehicles, such as submarines.
II. Balloon Configuration
FIG. 1 illustrates a high-altitude balloon 100, according to an
embodiment. The balloon 100 includes an envelope 102, a skirt 104,
and a payload 106.
The envelope 102 and the skirt 104 can take various forms, which
can be currently well-known or yet to be developed. For instance,
the envelope 102, the skirt 104, or both can be made of metalized
Mylar.RTM. or BoPET (biaxially-oriented polyethylene
terephthalate). Some or all of the envelope 102, the skirt 104, or
both can be constructed from a highly-flexible latex material or a
rubber material, such as, for example, chloroprene. These examples
are illustrative only; other materials can be used as well.
Further, the shape and size of the envelope 102 and the skirt 104
can vary depending upon the particular implementation.
Additionally, the envelope 102 can be filled with various different
types of gases, such as, for example, helium, hydrogen, or both.
These examples are illustrative only; other types of gases can be
used as well.
The payload 106 of the balloon 100 includes a processor 112 and
memory 114. The memory 114 can be or include a non-transitory
computer-readable medium. The non-transitory computer-readable
medium can have instructions stored thereon, which can be accessed
and executed by the processor 112 in order to carry out some or all
of the functions provided in this disclosure.
The payload 106 of the balloon 100 can also include various other
types of equipment and systems to provide a number of different
functions. For example, the payload 106 includes an optical
communication system 116. The optical communication system 116 can
transmit optical signals by way of an ultra-bright LED system 120.
In addition, the optical communication system 116 can receive
optical signals by way of an optical-communication receiver, such
as, for example, a photo-diode receiver system. Further, the
payload 106 can include an RF communication system 118. The RF
communication system 118 can transmit and/or receive RF
communications by way of an antenna system 140.
In addition, the payload 106 includes a power supply 126. The power
supply 126 can be used to provide power to the various components
of the balloon 100. The power supply 126 can be or include a
rechargeable battery. In some implementations, the power supply 126
can represent another suitable power supply known in the art for
producing power. In addition, the balloon 100 includes a solar
power generation system 127. The solar power generation system 127
can include solar panels, which can be used to generate power for
charging the power supply 126 or for distribution by the power
supply 126. In some embodiments, it may be desirable for the
balloon system to run off sustainable power. Therefore, all energy
used by the balloon system from power supply 126 may be provided
from a renewable source, such as solar power generation system
127.
Further, the payload 106 includes various types of sensors 128. The
payload 106 can include sensors such as, for example, video or
still cameras, a GPS system, motion sensors, accelerometers,
gyroscopes, compasses, or sensors for capturing environmental data.
These examples are illustrative only; the payload 106 can include
various other types of sensors. Further, some or all of the
components in the payload 106 can be implemented in a radiosonde,
which can be operable to measure various types of information, such
as, for example, pressure, altitude, geographical position
(latitude and longitude), temperature, relative humidity, wind
speed, or direction, among other information.
As noted above, the payload 106 includes an ultra-bright LED system
120. In some implementations, the ultra-bright LED system 120 can
be used for free-space optical communication with other balloons.
In some implementations, the ultra-bright LED system 120 can be
used for free-space optical communication with satellites. In some
implementations, the ultra-bright LED system 120 can be used for
free-space optical communication both with other balloons and with
satellites. To this end, the optical communication system 116 can
be configured to transmit a free-space optical signal by causing
modulations in the ultra-bright LED system 120. The manner in which
the optical communication system 116 is implemented can vary,
depending upon the particular application.
In addition, the balloon 100 can be configured for altitude
control. For instance, the balloon 100 can include a variable
buoyancy system. The buoyancy system can be configured to change
the altitude of the balloon 100 by adjusting the volume, the
density, or both of the gas in the envelope 102 of the balloon 100.
A variable buoyancy system can take various forms, and can
generally be any system that can change the volume and/or density
of gas in the envelope 102 of the balloon 100.
In an embodiment, a variable buoyancy system can include a bladder
110 that is located inside of the envelope 102. The bladder 110 can
be an elastic chamber that is configured to hold liquid and/or gas.
Alternatively, the bladder 110 need not be inside the envelope 102.
For instance, the bladder 110 can be a rigid bladder that can be
pressurized well beyond neutral pressure. The buoyancy of the
balloon 100 can therefore be adjusted by changing the density
and/or volume of the gas in the bladder 110. To change the density
in the bladder 110, the balloon 100 can be configured with systems
and/or mechanisms for heating and/or cooling the gas in the bladder
110. Further, to change the volume, the balloon 100 can include
pumps or other features for adding gas to and/or removing gas from
the bladder 110. To change the volume of the bladder 110, the
balloon 100 can include release valves or other features that are
controllable to allow gas to escape from the bladder 110. Multiple
bladders 110 can be implemented within the scope of this
disclosure. For instance, multiple bladders can be used to improve
balloon stability.
In an embodiment, the envelope 102 can be filled with helium,
hydrogen, or other material that is lighter than air. Thus, the
envelope 102 can have an associated upward buoyancy force. In this
embodiment, air in the bladder 110 can be considered a ballast tank
that can have an associated downward ballast force. In another
embodiment, the amount of air in the bladder 110 can be changed by
pumping air (for example, with an air compressor) into and out of
the bladder 110. By adjusting the amount of air in the bladder 110,
the ballast force can be controlled. In some embodiments, the
ballast force can be used, in part, to counteract the buoyancy
force and/or to provide altitude stability.
In some embodiments, the envelope 102 can be substantially rigid
and include an enclosed volume. Air can be evacuated from the
envelope 102 while the enclosed volume is substantially maintained.
In other words, at least a partial vacuum can be created and
maintained within the enclosed volume. Thus, the envelope 102 and
the enclosed volume can become lighter than air and provide a
buoyancy force. In some embodiments, air or another material can be
controllably introduced into the partial vacuum of the enclosed
volume by a control unit in an effort to adjust the overall
buoyancy force and/or to provide altitude control. Further, the
envelope 102 may be coupled to a mass-changing unit, configured to
function as the control unit. The mass-changing unit may be
configured with an impeller configured to add or remove air from
within the envelope 102. Additionally, the mass-changing unit may
also include a vent configured to add or remove air from the
envelope 102. A more detailed description of the altitude control
system is described with respect to FIG. 5 herein.
In an embodiment, a portion of the envelope 102 can be a first
color (for example, black) and/or a first material that is
different from another portion or the remainder of the envelope
102. The other portion or the remainder of the envelope can have a
second color (for example, white) and/or a second material. For
instance, the first color and/or first material can be configured
to absorb a relatively larger amount of solar energy than the
second color and/or second material. Thus, rotating the balloon
such that the first material is facing the sun can act to heat the
envelope 102 as well as the gas inside the envelope 102. In this
way, the buoyancy force of the envelope 102 can increase. By
rotating the balloon such that the second material is facing the
sun, the temperature of gas inside the envelope 102 can decrease.
Accordingly, the buoyancy force can decrease. In this manner, the
buoyancy force of the balloon can be adjusted by changing the
temperature/volume of gas inside the envelope 102 using solar
energy. In this embodiment, a bladder need not be an element of the
balloon 100. Thus, in this embodiment, altitude control of the
balloon 100 can be achieved, at least in part, by adjusting the
rotation of the balloon 100 with respect to the sun.
Further, the payload 106 of the balloon 100 can include a
navigation system (not shown in FIG. 1). The navigation system can
implement station-keeping functions to maintain position within
and/or move to a position in accordance with a desired topology. In
particular, the navigation system can use altitudinal wind data to
determine altitudinal adjustments that result in the wind carrying
the balloon in a desired direction and/or to a desired location.
The altitude-control system can then make adjustments to the
density of the balloon chamber in order to effectuate the
determined altitudinal adjustments and cause the balloon to move
laterally to the desired direction and/or to the desired
location.
Alternatively, the altitudinal adjustments can be computed by a
ground-based control system and communicated to the high-altitude
balloon. As another alternative, the altitudinal adjustments can be
computed by a ground-based or satellite-based control system and
communicated to the high-altitude balloon. Furthermore, in some
embodiments, specific balloons in a heterogeneous balloon network
can be configured to compute altitudinal adjustments for other
balloons and transmit the adjustment commands to those other
balloons.
In such an arrangement, the navigation system can be operable to
navigate the balloon to a landing location, in the event the
balloon needs to be removed from the network and/or accessed on the
ground. Further, a balloon can be self-sustaining so that it does
not need to be accessed on the ground. In some embodiments, a
balloon can be serviced in-flight by one or more service balloons
or by another type of service aerostat or service aircraft.
III. Balloon Networks
FIG. 2 illustrates a balloon network 200, according to an
embodiment. The balloon network 200 includes balloons 202A-202F.
The balloons 202A-202F are configured to communicate with one
another by way of free-space optical links 204A-204F. Configured as
such, the balloons 202A to 202F can collectively function as a mesh
network for packet-data communications. Further, at least some of
the balloons 202A-202F, such as, for example, the balloons 202A and
202B, can be configured for RF communications with a ground-based
station 206 by way of respective RF links 208A and 208B. The
ground-based station 206 represents one or more ground-based
stations. In addition, some of the balloons 202A-202F, such as, for
example, the balloon 202F, can be configured to communicate by way
of an optical link 210 with a ground-based station 212. The
ground-based station 212 represents one or more ground-based
stations.
In an embodiment, the balloons 202A-202F are high-altitude
balloons, which can be deployed in the stratosphere. At moderate
latitudes, the stratosphere includes altitudes between
approximately 10 kilometers (km) and 50 km above the Earth's
surface. At the poles, the stratosphere starts at an altitude of
approximately 8 km. In an embodiment, high-altitude balloons can be
configured to operate in an altitude range within the stratosphere
that has relatively low wind-speeds, such as, for example, between
5 and 20 miles per hour (mph).
In the high-altitude-balloon network 200, the balloons 202A-202F
can be configured to operate at altitudes between 18 km and 25 km.
In some implementations, the balloons 202A-202F can be configured
to operate at other altitudes. The altitude range of 18 km-25 km
can be advantageous for several reasons. In particular, this layer
of the stratosphere generally has relatively low wind speeds (for
example, winds between 5 and 20 mph) and relatively little
turbulence. Further, while the winds in this altitude range can
vary with latitude and by season, the variations can be modeled in
a reasonably accurate manner. In addition, altitudes above 18 km
are typically above the maximum flight level designated for
commercial air traffic. Therefore, interference with commercial
flights is not a significant concern when balloons are deployed
between 18 km and 25 km.
To transmit data to another balloon, a given balloon 202A-202F can
be configured to transmit an optical signal by way of a
corresponding optical link 204A-204F. In an embodiment, some or all
of the balloons 202A-202F can use one or more high-power
light-emitting diodes (LEDs) to transmit an optical signal.
Alternatively, some or all of the balloons 202A-202F can include
laser systems for free-space optical communications over
corresponding optical links 204A-204F. Other types of free-space
optical communication are possible. Further, in order to receive an
optical signal from another balloon by way of an optical link, a
given balloon 202A-202F can include one or more optical receivers,
as discussed above in connection with FIG. 1.
The balloons 202A-202F can utilize one or more of various different
RF air-interface protocols for communication with ground-based
stations, such as, for example, the ground-based station 206. For
instance, some or all of the balloons 202A-202F can be configured
to communicate with the ground-based station 206 using protocols
described in IEEE 802.11 (including any of the IEEE 802.11
revisions), various cellular protocols such as GSM, CDMA, UMTS,
EV-DO, WiMAX, and/or LTE, and/or one or more propriety protocols
developed for balloon-ground RF communication, among other
possibilities.
There can be scenarios where the RF links 208A-208B do not provide
a desired link capacity for balloon-ground communications. For
instance, increased capacity can be desirable to provide backhaul
links from a ground-based gateway. Accordingly, a balloon network
can also include downlink balloons, which can provide a
high-capacity air-ground link.
For example, in the balloon network 200, the balloon 202F is
configured as a downlink balloon. Like other balloons in the
balloon network 200, the downlink balloon 202F can be operable for
optical communication with other balloons by way of corresponding
optical links 204A-204F. The downlink balloon 202F can also be
configured for free-space optical communication with the
ground-based station 212 by way of the optical link 210. The
optical link 210 can therefore serve as a high-capacity link (as
compared to the RF links 208A-208B) between the balloon network 200
and the ground-based station 212.
Note that in some implementations, the downlink balloon 202F can be
operable for RF communication with the ground-based stations 206.
In other implementations, the downlink balloon 202F may only use
the optical link 210 for balloon-to-ground communications. Further,
while the arrangement shown in FIG. 2 includes one downlink balloon
202F, a balloon network can also include multiple downlink
balloons. In addition, a balloon network can be implemented without
the use of any downlink balloons.
In some implementations, a downlink balloon can be equipped with a
specialized, high-bandwidth RF communication system for
balloon-to-ground communications, instead of, or in addition to, a
free-space optical communication system. The high-bandwidth RF
communication system can take the form of an ultra-wideband system,
which can provide an RF link with substantially the same capacity
as one of the optical links 204A-204F.
Ground-based stations, such as the ground-based stations 206 and
212, can take various forms. Generally, a ground-based station
includes components such as transceivers, transmitters, and
receivers for communication with a balloon network by way of RF
links, optical links, or both. Further, a ground-based station can
use various air-interface protocols in order to communicate with
one or more of the balloons 202A-202F by way of an RF link. As
such, a ground-based station 206 can be configured as an access
point by which various devices can connect to the balloon network
200. The ground-based station 206 can have other configurations and
can serve other purposes without departing from the scope of this
disclosure.
Some or all of the balloons 202A-202F can be configured to
establish a communication link with space-based satellites by way
of corresponding communication links. The balloons can establish
the communication links with the space-based satellites in addition
to, or as an alternative to, the ground-based communication links.
In addition, the balloons can be configured to communicate with the
space-based satellites using any suitable protocol. In some
implementations, one or more of the communication links can be
optical links. Accordingly, one or more of the balloons can
communicate with the satellites by way of free-space optical
communication. Other balloon-satellite communication links and
techniques can be used.
Further, some ground-based stations, such as, for example, the
ground-based station 206, can be configured as gateways between the
balloon network 200 and another network. For example, the
ground-based station 206 can serve as an interface between the
balloon network 200 and the Internet, a cellular service provider's
network, or another network.
A. Mesh-Network Functionality
As noted above, the balloons 202A-202F can collectively function as
a mesh network. More specifically, because the balloons 202A-202F
can communicate with one another using free-space optical links,
the balloons can collectively function as a free-space optical mesh
network.
In a mesh-network configuration, each of the balloons 202A-202F can
function as a node of the mesh network. The mesh network can be
operable to receive data directed to it and to route data to other
balloons. As such, data can be routed from a source balloon to a
destination balloon by determining an appropriate sequence of
optical links between the source balloon and the destination
balloon. This disclosure may refer to these optical links,
collectively, as a "lightpath" for the connection between the
source and destination balloons. Further, this disclosure may refer
to each of the optical links as a "hop" along the lightpath.
To operate as a mesh network, the balloons 202A-202F can employ
various routing techniques and self-healing algorithms. In some
implementations, the balloon network 200 can employ adaptive or
dynamic routing, in which a lightpath between a source balloon and
a destination balloon is determined and set-up when the connection
is needed, and is released at a later time. Further, when adaptive
routing is used, the lightpath can be determined dynamically,
depending upon the current state, past state, and/or predicted
state of the balloon network.
In addition, the network topology can change as the balloons
202A-202F move relative to one another and/or relative to the
ground. Accordingly, the balloon network 200 can apply a mesh
protocol to update the state of the network as the topology of the
network changes. For example, to address the mobility of the
balloons 202A-202F, the balloon network 200 can employ and/or adapt
various techniques that are employed in mobile ad hoc networks
(MANETs).
In some implementations, the balloon network 200 can be configured
as a transparent mesh network. In a transparent balloon network,
the balloons can include components for physical switching in a way
that is entirely optical, without involving a substantial number
of, or any, electrical components in the physical routing of
optical signals. Accordingly, in a transparent configuration with
optical switching, signals can travel through a multi-hop lightpath
that is entirely optical.
In other implementations, the balloon network 200 can implement a
free-space optical mesh network that is opaque. In an opaque
configuration, some or all of the balloons 202A-202F can implement
optical-electrical-optical (OEO) switching. For example, some or
all of the balloons 202A-202F can include optical cross-connects
(OXCs) for OEO conversion of optical signals. This example is
illustrative only; other opaque configurations can be used.
The balloons 202A-202F in the balloon network 200 can utilize
techniques such as wavelength division multiplexing (WDM) in order
to increase link capacity. When WDM is implemented with transparent
switching, physical lightpaths through the balloon network can be
subject to the wavelength continuity constraint. In particular,
because switching in a transparent network is entirely optical, it
can be necessary, in some instances, to assign the same wavelength
to all optical links along a given lightpath.
An opaque configuration can be used to avoid the wavelength
continuity constraint. In particular, balloons in an opaque balloon
network can include OEO switching systems operable for wavelength
conversion. As a result, balloons can convert the wavelength of an
optical signal at corresponding hops along a lightpath.
Further, various routing algorithms can be employed in an opaque
configuration. For example, to determine a primary lightpath and/or
one or more diverse backup lightpaths for a given connection, a
balloon can apply shortest-path routing techniques, such as, for
example, Dijkstra's algorithm and k-shortest path. In addition, a
balloon can apply edge and node-diverse or disjoint routing, such
as, for example, Suurballe's algorithm. Further, a technique for
maintaining a particular quality of service (QoS) can be employed
when determining a lightpath.
B. Station-Keeping Functionality
In an embodiment, a balloon network 100 can implement
station-keeping functions to help provide a desired network
topology. For example, station-keeping can involve each of the
balloons 202A-202F maintaining a position or moving to a position
relative to one or more other balloons in the network 200. The
station-keeping can also, or instead, involve each of the balloons
202A-202F maintaining a position or moving to a position relative
to the ground. Each of the balloons 202A-202F can implement
station-keeping functions to determine the given balloon's desired
positioning in the desired topology, and if desirable, to determine
how the given balloon is to move to the desired position.
The network topology can vary depending on the desired
implementation. In an implementation, the balloons 202A-202F can
implement station-keeping such that the balloon network 200 has a
substantially uniform topology. For example, a given balloon can
implement station-keeping functions to position itself at
substantially the same distance (or within a certain range of
distances) from adjacent balloons in the balloon network. In
another implementation, the balloons 202A-202F can implement
station-keeping such that the balloon network 200 has a
substantially non-uniform topology. This implementation can be
useful when there is a need for balloons to be distributed more
densely in some areas than in others. For example, to help meet
higher bandwidth demands that are typical in urban areas, balloons
can be clustered more densely over urban areas than in other areas.
For similar reasons, the distribution of balloons can be denser
over land than over large bodies of water. These examples are
illustrative only; non-uniform topologies can be used in other
settings.
In addition, the topology of a balloon network can be adaptable. In
particular, balloons can utilize station-keeping functionality to
allow the balloons to adjust their respective positioning in
accordance with a change in the topology of the network. For
example, several balloons can move to new positions in order to
change a balloon density in a given area.
In an implementation, the balloon network 200 can employ an energy
function to determine whether balloons should move in order to
provide a desired topology. In addition, the energy function can
indicate how the balloons should move in order to provide the
desired topology. In particular, a state of a given balloon and
states of some or all nearby balloons can be used as inputs to an
energy function. The energy function can apply the states to a
desired network state, which can be a state corresponding to the
desired topology. A vector indicating a desired movement of the
given balloon can then be determined by determining a gradient of
the energy function. The given balloon can then determine
appropriate actions to take in order to effectuate the desired
movement. For example, a balloon can determine an altitude
adjustment or adjustments such that winds will move the balloon in
the desired manner.
C. Control of Balloons in a Balloon Network
Mesh networking, station-keeping functions, or both can be
centralized. For example, FIG. 3 illustrates a centralized system
for controlling a balloon network 304. In particular, a central
control system 300 is in communication with regional
control-systems 302A-302C. The central control system 300 can be
configured to coordinate functionality of the balloon network 304.
To this end, the central control system 300 can control functions
of balloons 306A to 306I.
The central control system 300 can communicate with the balloons
306A-306I by way of the regional control systems 302A-302C. Each of
the regional control systems 302A-302C can be a ground-based
station, such as, for example, the ground-based station 206
discussed above in connection with FIG. 2. Each of the regional
control systems 302A-302C can cover a different geographic area.
The geographic areas can overlap or be separate. Each of the
regional control systems 302A-302C can receive communications from
balloons in the respective regional control system's area. In
addition, each of the regional control systems 302A-302C can
aggregate data from balloons in the respective regional control
system's area. The regional control systems 302A-302C can send
information they receive to the central control system 300.
Further, the regional control systems 302A-302C can route
communications from the central control system 300 to the balloons
306A-306I in their respective geographic areas. For instance, the
regional control system 302A can relay communications between the
balloons 306A-306C and the central control system 300. Likewise,
the regional control system 302B can relay communications between
the balloons 306D-306F and the central control system 300.
Likewise, the regional control system 302C can relay communications
between the balloons 306G-306I and the central control system
300.
To facilitate communications between the central control system 300
and the balloons 306A-306I, some of the balloons 306A-306I can
serve as downlink balloons. The downlink balloons can communicate
with the regional control systems 302A-302C. Accordingly, each of
the regional control systems 302A-302C can communicate with a
downlink balloon in the geographic area that the regional control
system covers. In the balloon network 304, the balloons 306A, 306D,
and 306H serve as downlink balloons. The regional control system
302A can communicate with the downlink balloon 306A by way of
communication link 308A. Likewise, the regional control system 302B
can communicate with the downlink balloon 306D by way of
communication link 308B. Likewise, the regional control system 302C
can communicate with the balloon 306H by way of communication link
308C. The communication links 308A-308C can be optical links or RF
links, depending on the desired implementation.
In the balloon network 304, three of the balloons serve as downlink
balloons. In an implementation, all of the balloons in a balloon
network can serve as downlink balloons. In another implementation,
fewer than three balloons or more than three balloons in a balloon
network can serve as downlink balloons.
The central control system 300 can coordinate mesh-networking
functions of the balloon network 304. For example, the balloons
306A-306I can send the central control system 300 state
information. The central control system 300 can utilize the state
information to determine the state of the balloon network 304.
State information from a given balloon can include data such as,
for example, location data identifying the relative or absolute
location of the balloon. In addition, the state information from
the given balloon can include data representing wind speeds near
the balloon. In addition, the state information from the given
balloon can include information about an optical link that the
balloon has established. For example, the information about the
optical link can include the identity of other balloons with which
the balloon has established an optical link, the bandwidth of the
optical link, wavelength usage, or availability on an optical link.
Accordingly, the central control system 300 can aggregate state
information from some or all of the balloons 306A-306I in order to
determine an overall state of the balloon network 304.
The overall state of the balloon network 304 can be used to
coordinate mesh-networking functions, such as, for example,
determining lightpaths for connections. For example, the central
control system 300 can determine a current topology based on the
aggregate state information from some or all of the balloons
306A-306I. The topology can indicate which optical links are
available in the balloon network 304. In addition, the topology can
indicate which wavelengths are available for use with the links.
The central control system 300 can send the topology to some or all
of the balloons 306A-306I so that a routing technique can be
employed to select appropriate lightpaths (and possibly backup
lightpaths) for communications that use the balloon network
304.
In addition, the central control system 300 can coordinate
station-keeping functions of the balloon network 304. For example,
the central control system 300 can receive state information from
the balloons 306A-306I, as discussed above, and can use the state
information as an input to an energy function. The energy function
can compare the current topology of the network to a desired
topology and, based on the comparison, provide a vector indicating
a direction of movement (if any) of each balloon. Further, the
central control system 300 can use altitudinal wind data to
determine respective altitude adjustments that can be initiated in
order to achieve the movement towards the desired topology.
Accordingly, the arrangement shown in FIG. 3 provides for
coordinating communications between the central control system 300
and the balloon network 304. This arrangement can be useful to
provide centralized control for a balloon network that covers a
large geographic area. When expanded, this arrangement can support
a global balloon network, which can provide global coverage.
This disclosure contemplates arrangements other than the
arrangement shown in FIG. 3. For example, an arrangement can
include a centralized control system, regional control systems, and
sub-region systems. The sub-region systems can serve to provide
communications between the centralized control system and the
corresponding regional control systems. As another example, control
functions of a balloon network can be provided by a single,
centralized, control system. The control system can communicate
directly with one or more downlink balloons.
The central control system 300 and the regional control systems
302A-302C need not control and coordinate all of the functions of
the balloon network 304. In an implementation, a ground-based
control system and a balloon network can share control and
coordination of the balloon network. In another implementation, the
balloon network itself can control and coordinate all of the
functions of the balloon network. Accordingly, in this
implementation, the balloon network can be controlled without a
need for ground-based control. To this end, certain balloons can be
configured to provide the same or similar functions as those
discussed above in connection with the central control system 300
and the regional control systems 302A-302C.
In addition, control of a balloon network, coordination of the
balloon network, or both can be de-centralized. For example, each
balloon in a balloon network can exchange state information with
nearby balloons. When the balloons exchange state information in
this way, each balloon can individually determine the state of the
network. As another example, certain balloons in a balloon network
can serve as aggregator balloons. The aggregator balloons can
aggregate state information for a given portion of the balloon
network. The aggregator balloons can coordinate with one another to
determine the overall state of the network.
Control of a balloon network can be localized in a way that the
control does not depend on the overall state of the network. For
example, balloons in a balloon network can implement
station-keeping functions that only consider nearby balloons. In
particular, each balloon can implement an energy function that
takes into account the balloon's own state and the states of nearby
balloons. The energy function can be used to maintain the balloon
at a desired position or to move the balloon to a desired position
in relation to nearby balloons, without considering the desired
topology of the balloon network as a whole. When each balloon in
the balloon network implements an energy function in this way, the
balloon network as a whole can maintain a desired topology or move
towards a desired topology.
For example, assume that a given balloon B.sub.0 receives distance
information d.sub.1, d.sub.2, d.sub.3, . . . , d.sub.k. The
distance information d.sub.1 represents the distance from the
balloon B.sub.0 to its neighboring balloon B.sub.1. Likewise, the
distance information d.sub.2 represents a distance from the balloon
B.sub.0 to its neighboring balloon B.sub.2, the distance d.sub.3
represents a distance from the balloon B.sub.0 to its neighboring
balloon B.sub.3, and the distance d.sub.k represents a distance
from the balloon B.sub.0 to its neighboring balloon B.sub.k.
Accordingly, the distance information represents distances from the
balloon to its k closest neighbors. The balloon B.sub.0 can treat
the distance to each of the k balloons as a virtual spring with
vector representing a force direction from the first nearest
neighbor balloon i toward balloon B.sub.0 and with force magnitude
proportional to d.sub.i. The balloon B.sub.0 can sum each of the k
vectors to obtain a summed vector that represents desired movement
of the balloon B.sub.0. The balloon B.sub.0 can attempt to achieve
the desired movement by controlling its altitude, as discussed
above. This is but one technique for assigning force magnitudes;
this disclosure contemplates that other techniques can also be
used.
D. Balloon Network with Optical and RF Links Between Balloons
A balloon network can include super-node balloons (or simply "super
nodes") and sub-node balloons (or simply "sub-nodes"). The
super-nodes can communicate with one another by way of optical
links. The sub-nodes can communicate with super-nodes by way of RF
links. FIG. 4 illustrates a balloon network 400 that includes
super-nodes 410A-410C and sub-nodes 420A-420Q, according to an
embodiment.
Each of the super-nodes 410A-410C can be provided with a free-space
optical communication system that is operable for packet-data
communication with other super-node balloons. Accordingly,
super-nodes can communicate with one another by way of optical
links. For example, the super-node 410A and the super-node 410B can
communicate with one another by way of an optical link 402.
Likewise, the super-node 410A and the super-node 410C can
communicate by way of an optical link 404.
Each of the sub-nodes 420A-420Q can be provided with a
radio-frequency (RF) communication system that is operable for
packet-data communication over an RF air interface. In addition,
some or all of the super-nodes 410A-410C can include an RF
communication system that is operable to route packet data to one
or more of the sub-nodes 420A-420Q. For example, when the sub-node
420A receives data from the super-node 410A by way of an RF link,
the sub-node 420A can use its RF communication system to transmit
the received data to a ground-based station 430A by way of an RF
link.
In an embodiment, all of the sub-node balloons 420A-420Q can be
configured to establish RF links with ground-based stations. For
example, all of the sub-nodes 420A-420Q can be configured similarly
to the sub-node 420A, which is operable to relay communications
between the super-node 410A and the ground-based station 430A by
way of respective RF links.
In an embodiment, some or all of the sub-nodes 420A-420Q can be
configured to establish RF links with other sub-nodes. For example,
the sub-node 420F is operable to relay communications between the
super-node 410C and the sub-node 420E. In this embodiment, two or
more sub-nodes can provide a multi-hop path between a super-node
and a ground-based station. For example, a multi-hop path is
provided between the super-node 410C and the ground-based station
430E by way of the sub-node balloons 420E and 420F.
Note that an RF link can be a directional link between a given
entity and one or more other entities, or an RF link can be part of
an omni-directional broadcast. In the case of an RF broadcast, one
or more "links" can be provided by way of a single broadcast. For
example, the super-node 410A can establish a separate RF link with
each of the sub-nodes 420A-420C. Instead, the super-node 410A can
broadcast a single RF signal that can be received by the sub-nodes
420A, 420B, and 420C. The single RF broadcast can in effect provide
all of the RF links between the super-node balloon 410A and the
sub-node balloons 420A-420C.
Some or all of the super-nodes 410A-410C can serve as downlink
balloons. In addition, the balloon network 420 can be implemented
without the use of any of the sub-nodes 420A-420Q. In addition, in
an embodiment, the super-nodes 410A-410C can collectively function
as a core network (or, in other words, as a backbone network),
while the sub-nodes 420A-420Q can function as access networks to
the core network. In this embodiment, some or all of the sub-nodes
420A-420Q can function as gateways to the balloon network 400. Note
that some or all of the ground-based stations 430A-430L can also,
or instead, function as gateways to the balloon network 400.
The network topology of the balloon network 400 is but one of many
possible network topologies. Further, the network topology of the
balloon network 400 can vary dynamically, as super-nodes and
sub-nodes move relative to the ground, relative to one another, or
both.
IV. Methods for the Altitude Control for a Super Pressure
Aerostatic Balloon
FIG. 5 illustrates a method for the altitude control for a super
pressure aerostatic balloon. In particular, method 500 can be used
with the balloon systems previously discussed with respect to FIGS.
1-4, such as the balloon network 400 discussed above in connection
with FIG. 4. The method 500 may be used to reduce the power usage
of the balloon. By reducing the power usage of the balloon, the
flight time of the balloon may be extended. In some examples, a
pump associated with the balloon may use on the order of 300 Watts
of energy when operating. The pump may be one of the most
energy-expensive components of the balloon system. Therefore, by
minimizing the energy usage of the pump, the overall system energy
may be reduced by reducing the energy used by one of the most
energy-expensive component of the balloon system.
The energy usage of the pump may be reduced in several ways. First,
the pump may have an optimal operation mode. In the optimal
operation mode, the pump may be able to add air to the balloon in
the most energy efficient way. In some examples, the optimal
operation mode may specify a fill rate or operation speed of the
pump. In further examples, the optimal operation mode may be based
on a difference in pressure between the inside and outside of the
balloon. Second, the pump may be operated in a mode where it is
enabled and disabled with a timing to reduce the energy usage. This
mode will be discussed further with respect to method 500 below. In
another example, both the optimal operation mode and selectively
enabling and disabling the pump may be combined for efficient
operation.
Further, method 500 is presented in the context of adding mass to a
balloon to reduce the altitude. However, method 500 may also be
used with removing mass to increase the altitude of the balloon. In
some embodiments, method 500 may be performed at least in part by
the previously discussed centralized control system. However, the
balloon itself may perform some or all of method 500.
For example, method 500 may be performed by the centralized control
system described in FIG. 3. Note that by relying on such a
centralized control system, a balloon may reduce its power usage.
In another example, if a balloon detects the loss of the
communication link between the balloon and a centralized control
system or another system that is performing method 500 on behalf of
the balloon, then the balloon may take over for the control system
and perform some or all of method 500 on its own.
At block 502, the method 500 determines a target mass for a
variable-buoyancy vehicle, based on a target altitude for the
variable-buoyancy vehicle. In a super pressure system, the volume
of a balloon is relatively fixed. However, by adding or removing
air from the balloon, the system can adjust an internal pressure
within the balloon. The altitude at which the balloon flies is a
function of the pressure (and therefore mass) inside the balloon.
Thus, for any given altitude there is an associated balloon
pressure that is needed to fly at the given altitude. Thus, in an
example embodiment, block 502 may involve the balloon determining
the associated balloon pressure for flying at the target
altitude.
Note that as a precursor to block 502, the target altitude for the
balloon may be determined. Herein, the target altitude for a
balloon should be understood to be an altitude that a balloon
should move up or down to from its current altitude (assuming the
balloon is not already flying at the target altitude. The target
altitude may be determined by a fleet planning system or by another
system, based on various criteria. Alternatively, a balloon may
determine its own target altitude.
Once the target mass has been calculated at block 502, the target
mass can be compared to the present mass of the balloon. Based on
the difference between the target mass and the present mass, a
target change in mass may be calculated. To increase the altitude
of the balloon, the target mass will be less than the present mass.
To decrease the altitude of the balloon, the target mass will be
greater than the present mass.
Information about the current balloon mass and current altitude may
be obtained based on sensor data from the balloon sensors, such as
sensors 128. Sensor data may either be (i) provided from the
sensors to a processor or (ii) read from the sensor by the
processor (e.g. sensors may either be actively providing data or
they may passive sensors that must be read). The sensors may
provide information such as an ambient pressure and balloon
velocity. The ambient pressure sensor measures the air pressure in
the environment surrounding the balloon. The velocity sensor
provides data indicative of the velocity of the balloon. In some
embodiments, the velocity sensors may provide velocity with respect
to each axis in the three-axis coordinate system (e.g. an X-, Y-,
and Z-velocity).
Further, the sensors also provide location data. The location data
provides information relating to the location of the balloon. The
location data may be used to locate the balloon at a specific
position on the Earth (i.e. a global location). However, in other
embodiments, the location data may be data indicative of a relative
position. For example, a balloon may not know its exact global
location, but it knows its location with respect to another object
(or balloon). Thus, the location data from the sensors may be a
relative location.
In various embodiments, the sensor data may be received (or
measured) either continuously or periodically. Further, the sensor
data may be received either continuously or periodically. For
example, the rate at which sensor data is communicated may be based
on current balloon parameters, such as a current altitude and
velocity of the balloon. For example, if a balloon is configured to
hold a specific altitude, sensor data may be configured to be
received periodically. In one embodiment, sensor data is received
every 5 minutes. However, when the balloon is changing altitude,
sensor data may be configured to be received continuously.
Alternatively, when the balloon is changing altitude, sensor data
may be configured to be received with a shorter period than when
the balloon is holding a specific altitude. For example, sensor
data may be received every 30 seconds while the balloon is changing
altitude. The amount of time stated above for each example is
merely one example, other times may be used in each situation as
well.
In some embodiments, sensor data is first received by a processor
on the balloon and responsively transmitted wirelessly for further
processing. Before being transmitted for further processing, the
sensor data may be compressed for ease of transmission. The sensor
data may be transmitted to the centralized control system, as
previously discussed. In another embodiment, the sensor data may be
transmitted to a networked processing server, or other computing
device for further processing.
In some embodiments, a processor within the centralized control
system estimates current balloon parameters based on the received
sensor data. The balloon parameters include the current altitude
and vertical velocity of the balloon. Further, the balloon
parameters may also include the global location of the balloon as
well. Moreover, in some embodiments, the balloon parameters also
include the horizontal velocity. However, the horizontal velocity
may be omitted from the balloon parameters in various embodiments.
Thus, the balloon parameters may be considered to have a
1-dimension motion (e.g. position and speed along a vertical line,
perpendicular to the surface of the Earth) and a specific
location.
When the centralized control system receives the sensor data, it
will process the data to determine the balloon parameters. For
example, the output of the pressure sensor may be used to calculate
the altitude of the balloon. Additionally, a GPS sensor may provide
location data that can be used to help determine the balloon
parameters. Further, the output of the velocity sensors may be used
to determine the velocity component of the balloon parameters. The
centralized control system will compile the data from the various
sensors to determine the balloon parameters.
In some alternate embodiments, a processor that is mounted on the
balloon system estimates the balloon parameters. The processor may
estimate the balloon parameters and transmit the balloon parameter
information for further processing. Thus, in this embodiment the
balloon is configured to communicate processed parameter
information from the sensors, rather than the sensor data. The
processor on the balloon may calculate an estimated balloon
parameters in the same way as the centralized control system
estimates the balloon parameters. However, in other embodiments,
the processor on the balloon may use less computationally intensive
algorithms to calculate the balloon parameters. By using less
computationally intensive algorithms, the processor on the balloon
may use less power. The less computationally intensive algorithm
may either result in a less accurate parameter estimate (as
compared to the centralized control system estimate) or it may
result in the calculation being performed more slowly.
Additionally, block 502 may include either determining or receiving
desired final balloon parameters. Typically, the final balloon
parameters includes a new altitude for the balloon and zero
vertical movement (e.g. a parameter change for the balloon involves
changing the steady-state balloon altitude).
The final balloon parameters may be determined based on a variety
of factors. In one embodiment, the balloon parameters may be varied
based on ambient wind conditions. Wind conditions in the atmosphere
may vary greatly depending on altitude. Thus, it may be desirable
for the balloon to adjust its altitude to take advantage of wind
conditions. The balloon altitude may be adjusted based on a wind
speed, wind direction, or other criteria. The wind conditions that
evoke a change in balloon altitude may be the condition at the
current altitude, the desired altitude, or both. For example, wind
information may be communicated to the balloon in order to adjust
the altitude of the balloon to move the balloon to an altitude with
a wind in the correct direction to reposition the balloon.
In an additional embodiment, in some areas there may be
restrictions on the altitude at which a balloon can fly. When the
balloon approaches this area, final balloon parameters are
determined to ensure the balloon is flying within an appropriate
designated altitude. In another embodiment, the balloon may have a
radio link with other balloons, a ground base station, or a
satellite. Final balloon parameters may be determined in order to
adjust a radio link. In yet other embodiments, the final balloon
parameters may be determined based on external factors, such as
weather or other criteria. How exactly the final balloon parameters
are determined is not critical to the present application.
At block 504, the method 500 includes adding a first mass to the
balloon. The first mass added to the balloon is based on the target
change in mass. The first mass added is an amount of mass that is
less than the target change in mass. When the first mass is added,
it initially causes an increase in the internal pressure of the
balloon. In response to the increase in internal pressure of the
balloon, the balloon decreases altitude. However, the amount of the
first mass may be sufficient enough to cause the balloon to
decrease in altitude further than the steady-state altitude (as
shown, and will be later described with respect to, FIG. 6).
Because the movement of the balloon may cause it to overshoot the
steady-state altitude associated with the increase in mass, the
pressure within the balloon may fall below the initial
balloon-pressure in response to adding the first mass.
In order to perform the requested altitude adjustment, a parameter
model of the balloon may be created. The parameter model may have
at least 3 variables: (i) the mass of the balloon; (ii) the
vertical position of the balloon; and (iii) the vertical speed of
the balloon. Both the vertical position and the vertical speed of
the balloon are a function of the balloon's mass. The input to the
system a filling rate of the balloon; thus, the optimization
determines a fill-rate plan for the balloon. The output controlled
by the filling rate is the altitude of the balloon. Additionally,
the filling rate both (i) determines the balloon's mass and (ii) is
controlled with a mass-changing unit. The mass-changing unit is
configured to either add or remove air from the envelope of the
balloon to increase or decrease the balloon's mass. Air may be
added to the balloon with an impeller in the mass-changing unit.
The term "impeller" as used herein is to be broadly construed to
cover impellers, pumps, and any other devices that could be used to
force air towards the inlet ports.
Air may be removed from the balloon either with the impeller or a
vent in the mass-changing unit. To add air, the impeller creates a
pressure on a valve. When the pressure is greater than the valve
threshold, the valve opens, allowing mass in to the balloon. The
valve threshold is in part a function of the internal pressure of
the balloon. When the pressure in the balloon is lower, the valve
takes less pressure to open. When the valve is opened with less
pressure, the impeller can use less energy to add mass to the
balloon. Conversely, to remove air, the vent opens to release air
from the pressure within the balloon. Unlike the impeller, the vent
is generally a passive device. In some embodiments, the only energy
used by the vent is the opening and closing mechanism. Whereas the
impeller requires energy to operate.
In one embodiment, the air mass fill and release mechanism includes
an impeller housing disposed within a fixed housing, which in turn
is coupled to the balloon envelope. The impeller housing is
moveable relative to the fixed housing. The impeller housing and
the fixed housing form a seal in a closed position, whereas, in an
open position, the impeller housing defines an unobstructed airflow
passageway between an internal chamber in a balloon envelope and
the atmosphere. Air may be forced into the bladder with a pump or
impeller disposed in the impeller housing. Alternatively, air may
be forced out of the bladder with the pump or impeller or the air
may simply exit due to the pressure differential between the
bladder and atmosphere.
In addition, the impeller housing may creates efficiencies in air
flow by providing both an airflow seal and an unobstructed airflow
passageway between the balloon envelope and the atmosphere.
Specifically, in various embodiments, the impeller housing
comprises a hollow cylindrical body with a first end and a second
end and a plate having a periphery is coupled to the first end of
the impeller housing. A flange extends radially outward from the
impeller housing below the plate. A plurality of vents are defined
in the impeller housing between the plate and the flange, and the
airflow passageway is defined from the second end of the impeller
housing through the hollow cylindrical body of the impeller housing
to the second plurality of vents. An impeller or a pump is disposed
within the impeller housing between the first end and the second
end of the impeller housing.
In operation, the plate is movable relative to the fixed housing
from a closed position to an open position. For example, the
periphery of the plate mates with the periphery of the first end of
the fixed housing to form a seal in the closed position. In the
open position, the plate and at least a portion of the plurality of
vents in the impeller housing extend into the balloon envelope.
This open position provides fluid communication between atmosphere
and an internal chamber of the balloon envelope via the airflow
passageway in the impeller housing.
Further, when it is desired to add air to the bladder, the impeller
is turned on and air is forced towards the sealing plate prior to
moving the impeller housing into the open position. This prevents
air in the balloon envelope from prematurely evacuating. The fixed
housing beneficially provides a plurality of vents in its sidewall
to alleviate airflow back pressure on the impeller or pump before
the impeller housing is moved into the open position. Once the
spinning impeller reaches operating speed, one or more actuators
are activated. Activating the actuators causes the impeller housing
to disengage from the periphery of the first end of the fixed
housing. As a result of this disengagement, the seal between the
plate and the fixed housing is opened allowing air to move through
the airflow passageway between the atmosphere and the balloon. The
operating speed of the impeller is calculated such that the force
of the resulting airflow is greater than the force of the air mass
acting on the top surface of the plate (e.g., back pressure from
the bladder). When a desired quantity of air has been moved into
the bladder, the linear actuators are activated to lower the
impeller housing, while the impeller is still spinning.
In still other embodiments, the balloon includes provide a fill
mechanism that includes a passive valve system that does not
require electrical activation. In particular, a plate having one or
more inlet ports is provided that may be attached to the balloon
beneath the balloon envelope and the bladder positioned within the
balloon envelope. A housing is positioned beneath the plate having
an end that is positioned about the one or more inlet ports. A pump
or impeller is positioned within the housing that is used to force
air towards and through the one or more inlet ports in the plate
and into the bladder of the balloon.
When it is desired to add air to the bladder, the impeller is
turned on and air is forced towards the inlet ports in the plate.
The force of the air moved towards the inlet ports by the impeller
causes a pressure against the bottom of the umbrella valve. As the
impeller operates, the force on the bottom of the umbrella valve
caused by the air moved towards the inlet ports by the impeller
becomes greater than the force of the air pressure within the
bladder acting on the top of the umbrella valve, causing the
periphery of the umbrella valve to disengage from the periphery of
the inlet port. As a result of this disengagement, the seal between
the umbrella valve and the periphery of the inlet port is opened
allowing air to be forced through the inlet port and into the
bladder. The passive valve system provided herein allows the inlet
ports to be opened and closed without requiring electrical
actuation of a valve, therefore eliminating the possibility of an
electrical malfunction. In addition, the inlet ports may be opened
and closed without requiring a valve having moving parts, therefore
eliminating the possibility of having a valve that becomes "stuck"
in an open or closed position. As a result, reliable operation of
the air mass fill mechanism may be provided throughout the extreme
temperatures that are encountered in operation.
At Block 506, a second mass is added to the balloon in response to
the pressure in the balloon dropping below a threshold. As
previously discussed, when the first mass is added to the balloon,
the pressure inside the balloon increase causing the balloon
altitude to decrease. While the balloon is moving from its initial
altitude to the steady-state altitude associated with the added
first mass, it may overshoot the steady-state altitude of the
balloon with the initial mass plus the added first mass. As the
altitude of the balloon decreases, the pressure within the balloon
decreases as well. As the balloon altitude decreases, it may
overshoot the steady-state altitude associated with the mass
increase. When the balloon overshoots the steady-state altitude,
the pressure within the balloon may be lower the initial balloon
pressure, and the balloon will naturally rise back towards the
steady-state altitude. However, this drop in pressure also makes it
easy or for the impeller to add mass the balloon (due to the valve
threshold decreasing in response to the decrease in balloon
pressure). Because it is easier to add mass to the balloon, the
impeller will use less energy to add the second mass (as compared
to if the same amount of mass was added at the same time the first
mass was added).
Put in simpler terms, by adding the first mass, waiting period of
time for the pressure to drop within the balloon, and adding a
second mass, the total amount of energy used to add the total mass
will be less than the amount of energy needed to add the total mass
at once. Thus, the balloon will move a more energy efficient
manner.
The total amount of energy required adding mass to the balloon
changes because of a change in differential pressure (i.e. the
difference in pressure between the air inside of the balloon and
the air external to the balloon) as the altitude of the balloon
moves. Typically, the inside of the balloon has a higher pressure
than the outside of the balloon. When the first mass is added to
the balloon, the balloon will decrease in altitude. As the balloon
decreases in altitude, the balloon will also cool down. This
cooling of the balloon (and the air inside the balloon) causes the
differential pressure between the inside of the balloon and the
outside of the balloon to decrease. As the differential pressure
decreases, air can be added to the balloon more easily.
In one example, the ambient temperature of the air surrounding the
balloon may be 216 Kelvin (K). The inside of the balloon may be
approximately 236 K to 246 K. Because air pressure is a function of
temperature, the inside of the balloon has a higher pressure than
the air outside the balloon. The balloon system may cause the pump
to add mass to the balloon. In one embodiment, mass may be added as
a given rate, such as 5 grams per second, in order to make the
balloon decrease altitude over a threshold amount, such as 100
meters. In another embodiment, mass may be added as a given rate,
such as 5 grams per second, in order to make the balloon decrease
altitude at a rate of 1 meter per second. Further, as the balloon
changes altitude, the temperature inside of the balloon may change
from approximately 236 K to 246 K down to about 221 K to 226 K. The
temperature change of the inside of the balloon represents
approximately a 10% change in absolute temperature of the inside of
the balloon.
In both example embodiments, the balloon may continue to decrease
in altitude until the temperature outside of the balloon is within
5 degrees of the internal pressure of the balloon. Thus, as the
temperature difference decreases, so does the differential
pressure. As the differential pressure decreases, the amount of
energy needed to add mass to the balloon decreases as well. In some
additional examples, the balloon may be configured to adjust the
altitude in a relatively quick manner, such as decreasing in about
5 minutes, in order for any other thermal effects to be
mitigated.
In some embodiments, the balloon will actively monitor the pressure
within the balloon and only add the mass once the pressure falls
below the threshold. Active monitoring maybe a continuous
monitoring of the pressure or a periodic monitoring the pressure,
such as monitoring the balloon every few seconds (or minutes). In a
different embodiment, a computer system can predict the pressure in
the balloon as a function of time (after the first mass is added).
In this embodiment the balloon will wait a determined amount of
time before adding the second mass. The amount of time is equal to
an amount of time the computer predicts it will take for the
pressure to fall approximately to the threshold pressure.
FIG. 6 illustrates an example parameter chart 600 describing the
internal pressure 602 and altitude 612 of a balloon changing
altitudes. The example shown in FIG. 6 is one example of the
operation of present disclosure. The exact curves are not mandatory
to practice the disclosure but show one set of operating
conditions. The output of the system is given by chart 612. In the
present system, the output is the altitude of the balloon. Chart
602 shows the variable to the system. Here, the variable is
internal pressure of the balloon.
In the example shown by chart 600, at a time T0, the balloon has an
initial pressure as indicated by line 606 and an altitude indicated
by line 616. At time T0, the impeller begins to add the first
amount of mass to the balloon. Mass is added by the impeller from
time T0 until time T1. As mass is being added, the pressure in the
balloon (as shown by curve 604) increases and the balloon decreases
in altitude (as shown by curve 614).
At time T1, the impeller stops adding mass to the balloon. In
response to the mass in the balloon no longer changing, the
pressure in the balloon begins to decline as the balloon drops in
altitude. From time T1 until time T2, the balloon has an internal
pressure greater than the initial pressure. At time T2, the
internal pressure in the balloon is equal to the initial pressure
in the balloon. This is due to the new altitude of the balloon, as
indicated by curve 614.
Between time T2 and time T3, the balloon has an internal pressure
that is less than the initial pressure of the balloon. However, the
balloon has yet to reach the threshold pressure. Additionally,
between time T2 and time T3, the balloon's altitude continues to
decrease. The balloon's altitude continues to decrease because the
movement from one altitude to another may include a bit of on
oscillation while the balloon settles at the steady-state altitude.
During normal operation, after mass is added (or removed) the
balloon will oscillate around the new altitude for a period of time
before it settles on the final altitude. In the present disclosure,
there is no oscillation shown because additional mass is added
before the first oscillation cycle is complete.
At time T3, the balloon reaches the threshold pressure 608. When
the threshold pressure 608 is met, the impeller begins to add more
mass to the balloon in order to reach the target balloon mass.
Because the internal pressure at time T3 is below the pressure at
time T0, the impeller uses less energy to add mass to the balloon
when the balloon has the lower pressure, therefore saving energy.
After time T3, the pressure in the balloon increases. Additionally,
in the embodiment shown in FIG. 6, the altitude of the balloon
begins to steady as more mass is added. The final steady-state
altitude is not shown as part of FIG. 6.
Additionally, the line 622 shows what would have happened to the
pressure in the balloon if the second mass were not added at time
T3. There would have been an oscillation of the internal pressure
within the balloon. Additionally, line 624 shows what the altitude
of the balloon would have done if the second mass was not added at
time T3. As shown by line 624, the altitude of the balloon would
have increased after time T3. The altitude would have oscillated
around the steady state altitude associated with the mass of the
balloon including the first added mass.
In the example shown in FIG. 6, the threshold pressure 608 is one
example of a threshold pressure. In various embodiments, the
threshold pressure 608 may be determined in various ways. For
example, the threshold pressure 608 may be determined to be a
percentage of the initial pressure (e.g., the threshold is met when
the internal pressure of the balloon drop by 3% from the initial
pressure). In another example, the threshold pressure 608 may be
determined based on the pressure curve (e.g., curve 604). The
threshold may be met when the pressure curve has a first derivative
that is approximately zero and the second derivative is positive.
This would indicate when the balloon has reached a minimum of the
internal pressure. In yet another example, the threshold may be an
inflection point of the curve 604. An inflection point is the point
where the second derivative changes sign from positive to negative
(or negative to positive). In various other embodiments, the
threshold pressure 608 may be set in a variety of other ways.
There are various other ways the altitude of the balloon may be
adjusted. Similar to that shown in FIG. 6, the balloon may move in
a manner that may be plotted on a parameter chart similar to
parameter chart 600. As disclosed herein, the present disclosure
includes adding a first amount of mass and adding a second amount
of mass when the internal pressure decreases below a threshold. The
specific movement shown in FIG. 6 is not meant to be a limiting
movement.
V. Computing Device and Computer Program Product
FIG. 7 illustrates a functional block diagram of a computing device
700, according to an embodiment. The computing device 700 can be
used to perform functions in connection with adjusting the altitude
of a balloon in a balloon network. In particular, the computing
device can be used to perform some or all of the functions
discussed above in connection with FIGS. 1-6.
The computing device 700 can be or include various types of
devices, such as, for example, a server, personal computer, mobile
device, cellular phone, custom computing device, or tablet
computer. In a basic configuration 702, the computing device 700
can include one or more processors 710 and system memory 720. A
memory bus 730 can be used for communicating between the processor
710 and the system memory 720. Depending on the desired
configuration, the processor 710 can be of any type, including a
microprocessor (.mu.P), a microcontroller (.mu.C), or a digital
signal processor (DSP), among others. A memory controller 715 can
also be used with the processor 710, or in some implementations,
the memory controller 715 can be an internal part of the processor
710.
Depending on the desired configuration, the system memory 720 can
be of any type, including volatile memory (such as RAM) and
non-volatile memory (such as ROM, flash memory). The system memory
720 can include one or more applications 722 and program data 724.
The application(s) 722 can include an index algorithm 723 that is
arranged to provide inputs to the electronic circuits. The program
data 724 can include content information 725 that can be directed
to any number of types of data. The application 722 can be arranged
to operate with the program data 724 on an operating system.
The computing device 700 can have additional features or
functionality, and additional interfaces to facilitate
communication between the basic configuration 702 and any devices
and interfaces. For example, data storage devices 740 can be
provided including removable storage devices 742, non-removable
storage devices 744, or both. Examples of removable storage and
non-removable storage devices include magnetic disk devices such as
flexible disk drives and hard-disk drives (HDD), optical disk
drives such as compact disk (CD) drives or digital versatile disk
(DVD) drives, solid state drives (SSD), and tape drives. Computer
storage media can include volatile and nonvolatile, non-transitory,
removable and non-removable media implemented in any method or
technology for storage of information, such as computer readable
instructions, data structures, program modules, or other data.
The system memory 720 and the storage devices 740 are examples of
computer storage media. Computer storage media includes, but is not
limited to, RAM, ROM, EEPROM, flash memory or other memory
technology, CD-ROM, DVDs or other optical storage, magnetic
cassettes, magnetic tape, magnetic disk storage or other magnetic
storage devices, or any other medium that can be used to store the
desired information and that can be accessed by the computing
device 700.
The computing device 700 can also include output interfaces 750
that can include a graphics processing unit 752, which can be
configured to communicate with various external devices, such as
display devices 790 or speakers by way of one or more A/V ports or
a communication interface 770. The communication interface 770 can
include a network controller 772, which can be arranged to
facilitate communication with one or more other computing devices
780 over a network communication by way of one or more
communication ports 774. The communication connection is one
example of a communication media. Communication media can be
embodied by computer-readable instructions, data structures,
program modules, or other data in a modulated data signal, such as
a carrier wave or other transport mechanism, and includes any
information delivery media. A modulated data signal can be a signal
that has one or more of its characteristics set or changed in such
a manner as to encode information in the signal. By way of example,
and not limitation, communication media can include wired media
such as a wired network or direct-wired connection, and wireless
media such as acoustic, radio frequency (RF), infrared (IR), and
other wireless media.
The computing device 700 can be implemented as a portion of a
small-form factor portable (or mobile) electronic device such as a
cell phone, a personal data assistant (PDA), a personal media
player device, a wireless web-watch device, a personal headset
device, an application specific device, or a hybrid device that
include any of the above functions. The computing device 700 can
also be implemented as a personal computer including both laptop
computer and non-laptop computer configurations.
The disclosed methods can be implemented as computer program
instructions encoded on a non-transitory computer-readable storage
medium in a machine-readable format, or on other non-transitory
media or articles of manufacture. FIG. 8 illustrates a computer
program product 800, according to an embodiment. The computer
program product 800 includes a computer program for executing a
computer process on a computing device, arranged according to some
disclosed implementations.
The computer program product 800 is provided using a signal bearing
medium 801. The signal bearing medium 801 can include one or more
programming instructions 802 that, when executed by one or more
processors, can provide functionality or portions of the
functionality discussed above in connection with FIGS. 1-6. In some
implementations, the signal bearing medium 801 can encompass a
computer-readable medium 803 such as, but not limited to, a hard
disk drive, a CD, a DVD, a digital tape, or memory. In some
implementations, the signal bearing medium 801 can encompass a
computer-recordable medium 804 such as, but not limited to, memory,
read/write (R/W) CDs, or R/W DVDs. In some implementations, the
signal bearing medium 801 can encompass a communications medium 805
such as, but not limited to, a digital or analog communication
medium (for example, a fiber optic cable, a waveguide, a wired
communications link, or a wireless communication link). Thus, for
example, the signal bearing medium 801 can be conveyed by a
wireless form of the communications medium 805 (for example, a
wireless communications medium conforming with the IEEE 802.11
standard or other transmission protocol).
The one or more programming instructions 802 can be, for example,
computer executable instructions. A computing device (such as the
computing device 700 of FIG. 7) can be configured to provide
various operations in response to the programming instructions 802
conveyed to the computing device by one or more of the
computer-readable medium 803, the computer recordable medium 804,
and the communications medium 805.
While various examples have been disclosed, other examples will be
apparent to those skilled in the art. The disclosed examples are
for purposes of illustration and are not intended to be limiting,
with the true scope and spirit being indicated by the following
claims.
* * * * *